Something similar happened when my brother got married. He and his fiancee only wanted people who were close to the couple as a whole - not individually - in the wedding. I was asked, as was my eldest brother who is closer to them in age. Our other brother, one who was not very family-oriented and lived far away, was not.

That brother and I are the half siblings of the other two brothers, so we've always felt a little disconnected. My brother made it clear he didn't want that brother (let's call him Jerry) in the wedding because Jerry hadn't spent much time with his fiancee and it wouldn't make sense to have him in the wedding. This broke my father's heart. He understood that it was my brother's wedding, but asking two of the siblings to be in and not the third was not fair. My brother and his fiancee were very confident in not wanting him in the wedding, but after talking to my dad, they changed their minds and realized they were being unfair.

Two different situations/people. I guess I'm trying to say, I understand both sides. Weddings should be for the people that are getting married, but often times, this is not the case. If you think this is something that will alienate your sisters/side of the family, I urge you not to do it. Families can be difficult, but my other brother (I know, I have a lot - the eldest brother) got married and none of us were even invited (for really complicated reasons I won't go into). That killed us.

Weddings aren't just about the couple, it's a family occasion and while I completely support you making your own decisions on who you want in the wedding (I personally hate wedding politics) think hard before making a decision that will piss of your family. I've been the sister of two brothers who have gotten married, one I was in the wedding for and one I wasn't even invited to. The sister-in-law that asked me to be in the wedding is now someone I'm super close with. The one that didn't care either way is not accepted or liked by my family. Your fiancee is becoming part of your family, whether she likes it or not, so if she wants to be accepted by them, she needs to take the initiative and show she cares enough to include them. Weddings are not worth causing rifts in family's for.

But again, I completely support your decision. Do what feels right. I just don't want you to end up with my family situation, not even speaking because of all the wedding politics. Not worth it.